Tom Glasgow: Collards, other crucifers are susceptible to black rot

Cabbage, broccoli, cauliflower, Brussels sprouts, Chinese cabbage, kale, radish, turnip, mustard, rutabaga and the indispensable collards are all members of the crucifer family (Brassicaceae). This group represents the lionís share of plantings in most local cool season gardens, and is certainly well suited to our fall and wi...

Cabbage, broccoli, cauliflower, Brussels sprouts, Chinese cabbage, kale, radish, turnip, mustard, rutabaga and the indispensable collards are all members of the crucifer family (Brassicaceae). This group represents the lionís share of plantings in most local cool season gardens, and is certainly well suited to our fall and winter weather conditions. However, disease problems are a possibility, especially in sites where crucifers have been grown consistently over a period of years.

Black rot, caused by a Xanthomonas bacterium, is one of the most common and devastating disease problems found on crucifer crops, and is worth knowing about if these plants are an important part of your year to year gardening activities.

Suspect black rot if you notice yellowing at the leaf margins, followed by the development of yellow to yellow-orange V-shaped lesions that expand into the leaves from the margins. You may also notice black leaf veins in the infected area, and a bacterial ooze coming out of leaf lesions.

According to a note from Cornell University, the bacterial infection becomes systemic, meaning that it can enter the veins of the plant and spread into the head. This, of course, leads to head rot either in the field or in storage.

Black rot is a difficult disease problem to manage, and chemical control is not feasible in home gardens. If black rot is confirmed in a garden, the best course of action is to move production to a new piece of ground, or to a garden where no crucifers were grown during the previous two or three years. If you are establishing a new garden, try to avoid poorly drained or shady locations.

Unfortunately, itís easy to move inoculum from one site to another on garden tools, your boots, wheels of garden carts or similar means. The bacterium can also be spread by laterally moving surface water during heavy rains, splashing water, windblown water droplets and animals. So thereís no guarantee that selecting a new site elsewhere on your property will solve the problem, but as always, we just do our best and hope for good results.

Feel free throughout the next few months to submit suspicious foliage from collards or other crucifers to your nearest Cooperative Extension office. In some cases additional material may be needed, or a submission made to the Plant Disease and Insect Clinic at N.C. State.

In comparison to serious issues such as black rot on crucifers, spittlebugs on muscadine grape vines are an unwelcome site, but nothing to be alarmed about. You probably have spittlebug larvae if you notice spittle-like masses along the vine, and on foliage and maturing grapes. Spittlebugs are considered harmless to our muscadines, although they can spread Pierceís Disease on bunch grapes.

If you wish to clean up the mess, avoid insecticide use on those rapidly maturing muscadine grapes and simply dislodge the critters with a strong stream of water from the water hose. The larvae are well protected by the spittle anyway, so insecticide sprays would likely provide very little control.

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Tom Glasgow is the Craven County Extension director. Contact him at tom_glasgow@ncsu.edu.